In electrically transmitting image data from an image-carrying medium, it is difficult to place the image-carrying medium such as a sheet of paper at a predetermined orientation with respect to a scanner of a data transmitting device. As a result of inaccurate placement of the image data, at a receiving end of the electronic transmission, the image data is rotated or misplaced. This misplacement of the image data is not only aesthetically unpleasant, but also causes a data entry problem if the transmitted image is used to generate a data entry signal for a computer system. For example, referring to FIG. 1A, a customer uses a predetermined standard data entry order form to order 100 units of a products A, 500 units of a product B and 1000 units of a product C. The customer faxes the above described order form, and as indicated by a dotted line a certain quantity such as 100 units is located at a predetermined position in the order form. However, according to this example, the order form is accidentally placed upon transmission. As a result, the received order form on an image carrying medium or the received order form image is at an angle as shown in FIG. 1B. Although an area as indicated in the dotted line is scanned for determining a quantity of the product A, an image of the numerical figures for the intended quantity is not located in the expected area due to the misplacement. To correct the above described problem, prior art attempts included the following approaches.
According to a first approach, Japanese Laid Publication 63-3388 discloses a positional correction method using template matching which gradually changes the position of a template with respect to an input image in the X and Y directions. At each position, a matching score is generated to reflect how close the input image portion matches the template. Based upon the matching scores at the various positions, a vector is determined for correcting the position of the input image.
According to a second approach, Japanese Patent 2-54495 discloses a positional correction method based upon bit or on-pixel counts in the X and Y directions. The number of on-bits in each row and column of an input image as well as a standard image respectively is counted. Based upon the comparison of these bit counts between the input image and the standard image, an amount of positional adjustments is determined. The above determined positional amount is to minimize the discrepancy in the bit count between the input image and the standard image.
According to a third approach Japanese Laid Publication 4-261259 discloses a rotational correction method. While one way of determining an amount of rotational discrepancy is a user input via a pointing device, another way is to automatically determine the discrepancy using a predetermined set of marks or location indicators in an input image and a standard image. Japanese Laid Publications 53-48059 and 7-101438 also disclose the use of a predetermined set of marks such as timing marks at specified locations on a sheet of paper for scanning information in the forms.
According to a fourth approach, Japanese Laid Publication 4-336677 and 4-261259 discloses a correction method based upon corresponding points which are determined by an user input via a pointing device or are automatically determined in an input image and a standard image. Subsequently, input image areas are determine to include these corresponding points in the input image. To determine an amount of correction for placing the input image at a desirable position, the input image areas are moved with respect to those in the standard image for a best match.
For the above described approaches which employ corresponding pairs of predetermined marks, Japanese Patent 59-218573 discloses a method of removing certain corresponding pairs of markers before determining an amount of positional adjustments in order to improve the accuracy of such adjustments.
The above described prior attempts are either computation intensive or require an additional predetermined marker on a data entry form. In the first and fourth approaches, an input image is variously positioned at a predetermined interval with respect to a standard image, and at each position, a computation-intensive pattern matching process is performed. Although the positional interval is adjusted to control the number of repetition, the larger the interval is, the less accurate the pattern matching process becomes.
As to the second approach, the accuracy of pattern matching is affected by rotation, enlargement or reduction of an input image. Japanese Patent 63-212269 discloses one way to take the above described scaling issue into consideration by determining a scale factor based upon a corresponding pair of predetermined marks.
Lastly, as to the third approach, an additional location marker is necessary for automatically determining an amount of correction. Such additional markers are generally undesirable since they occupy areas in the data entry form. In order to rely upon these location markers to determine an accurate amount of positional correction, a relatively large number of these markers is necessary. Even though a large number of marks is used, if these marks are relatively inconspicuous for improving the above described appearance concern, erroneous detections of these marks become a problem for determining an amount of positional correction.
For these above described and other reasons, the prior art attempts do not provide a satisfactory method or system for correcting the positional location of an input image which has been inputted via an image inputting device such as a scanner.